Capsulotomy device

ABSTRACT

A surgical device and procedure are provided for smoothly and easily accessing tissue to perform microsurgery, including a capsulotomy of a lens capsule of an eye. The device includes a handpiece with a tip for insertion into an incision in the cornea of the eye. A sliding element is disposed within the handpiece and a suction cup is mounted to the sliding element. The sliding element can be translated to move the suction cup into and out of the handpiece. A compression mechanism associated with the suction cup and the handpiece compresses the suction cup for deployment through the tip of the handpiece. The suction cup can expand inside the anterior chamber into a cutting position on the lens capsule. A cutting element mounted to the suction cup is used to cut a portion of the lens capsule and to remove the portion from the eye. The cutting element may be mounted to a cutting element support structure in a way that prevents heating of the device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/353,220, with a 371(c) date of Apr. 21, 2014, now U.S. Pat. No.10,206,816 issued on Feb. 19, 2019, which is a National Stage Entry ofInternational Application No. PCT/US2012/061361 filed on Oct. 22, 2012,which claims the benefit of U.S. Provisional Patent Application No.61/550,111, filed Oct. 21, 2011, both of which are incorporated hereinby reference in their entirety for all purposes.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with government support under Grant Numbers3R44EY021023-03S1, 5R44EY021023-03, 1R43EY021023-01A1, 2R44EY021023-04,and 2R44EY021023-02, awarded by the National Institutes of Health. Thegovernment has certain rights in the invention.

BACKGROUND

This invention pertains in general to microsurgery of tissue, and morespecifically to procedures and devices for accessing a tissue throughanother tissue layer, to cut or otherwise manipulate that tissue. Forexample, the procedures and devices can be used to deliver an ophthalmicsurgical device through the cornea to the anterior lens capsule membranein the anterior chamber of an eye.

Lens cataract is the leading cause of blindness worldwide and surgicaltreatment by cataract removal is the treatment of choice. A cataract isa clouding that develops in the lens of the eye or in its envelope. Thecreation of areas of opacity in the lens obstructs the passage of light.The lens of the eye is supposed to be transparent. If the lens developsopaque areas, as in a cataract, the lens must be surgically removed. Ifno lens is present in the eye, corrective glasses are required to focusan image on the retina. The lens, however, can be replaced with anartificial intraocular lens (IOL) to provide better vision aftercataract removal. There may also be other reasons such as presbyopia toreplace a lens that is not serving its functions appropriately.

The removal of the lens for replacement with an IOL is a surgicalprocedure that requires substantial precision. The lens is completelyenclosed by a membrane called the lens capsule, so the surgeon mustfirst cut through the capsule to access the lens. It is important to cutthe capsule in just the right way. If the lens capsule has been cutcorrectly, and not damaged during the cataract removal, then it can beused to hold an IOL. The implantation of an IOL requires the creation ofan opening in the lens capsule that is precisely centered, sized, andshaped for implant stability and for optimal IOL function. The matchingof the lens capsule opening size to the peripheral margins of the IOL iscritical. The goal of the surgeon is to create a perfectly circular(e.g., 5.5+/−0.1 mm diameter) hole in the capsular membrane (i.e., thelens capsule) that encapsulates the lens, centered on the optical axisof the eye, with no tears or defects in the edge of the hole. Tears ordefects on the edge of the hole make the capsule very weak andvulnerable to losing the ability to hold the IOL properly. Different IOLdesigns may require a different diameter for the hole (e.g., rangingfrom 4.5+/−0.1 mm to 6.0+/−0.1 mm), but whatever the prescribed diameteris, the accuracy of the surgeon in actually achieving it is veryimportant for proper outcome of the cataract surgery. This is especiallytrue of IOLs intended to perform complex optical and focusing functions.

Creating an opening in the lens capsule with this required level ofprecision is a difficult task for a surgeon controlling and guidingconventional handheld cutting instruments and attempting to trace aprecise circular route on the lens capsule. Currently, to perform acapsulotomy (the creation of an opening in the lens capsule), thesurgeon typically manually creates a small tear in the anterior regionof the lens capsule. With great caution, the surgeon then uses a smallforceps to try to extend the edge of the tear so as to follow a circularpath of the specified diameter and centered on the optic axis of theeye. In practice, it often happens that the hole does not end upcircular, or the correct diameter, or centered on the optic axis. Therecan also be radial tears in the edge of the hole that greatly weaken thecapsule. As a result of any of these errors, the capsule may not be ableto hold the IOL properly, and optimal visual outcome cannot be achieved.

In addition to the difficulties faced by the surgeon in accessing thelens by performing a precise capsulotomy of the lens capsule, thesurgeon must also be able to access the lens capsule itself. The lens ispositioned in the anterior chamber of the eye. To access the lenscapsule, the surgeon must create an incision in the cornea and carefullyinsert the capsulotomy instruments through this incision. The samerequirement exists in a number of microsurgery procedures in which anincision in a first layer of tissue must be passed through before asecond layer of tissue, behind or beneath that first layer, can beaccessed. For the surgeon to maneuver the microsurgery instrumentsthrough the corneal incision, the incision must be of sufficient size toaccommodate these instruments. However, the larger the incision, thegreater the risk of infection, of corneal distortion, astigmatism, andof other complications. Microsurgery instruments commonly are notcompact enough or are not sufficiently streamlined in shape, making itdifficult for the surgeon to minimize the incision size or possiblyrisking tears or other damage at the incision site. Cutting elements orother sharp components are sometimes exposed during insertion, requiringthe surgeon to be very precise and creating further risk of collateraldamage to tissue when inserting the instrument through the incision.Further, this insertion often requires multiple steps and sometimescomplex maneuvering of instruments by the surgeon, leaving little roomfor error. Once inserted, instruments are often not easily manipulatedand the surgeon may be forced to handle and move multiple separatepieces in a small space. Any of these problems can make it verydifficult for a surgeon to access a second layer of tissue behind afirst layer, particularly when the second layer is tissue in a verysmall area, such as within the eye.

Given the drawbacks of existing treatment devices/procedures foraccessing tissue, such as the lens capsule, to perform surgery, improvedtechniques and devices for performing microsurgery are needed.

SUMMARY

Embodiments of the invention include devices and methods for accessing alens capsule through a cornea of an eye, for performing a capsulotomy inthe eye. In one embodiment, provided herein is a capsulotomy device foraccessing a lens capsule through a cornea of an eye, the devicecomprising: an elastomeric structure; a support structure mounted to theelastomeric structure; and a cutting element extending from the supportstructure that is mounted to the elastomeric structure, wherein thecutting element and the elastomeric structure are not in physicalcontact.

In an embodiment, the cutting element is an electrode, and the devicecomprises one or more electrical elements for delivering current to anelectrical lead connected to the electrode to heat the electrode forexcising a portion of tissue of the lens capsule. In some embodiments,the electrode is circular. In certain embodiments, the electrodecomprises a continuous element and the device further comprises a firstand second connecting trace connecting the electrical lead to theelectrode, wherein the connecting traces are positioned on oppositesides of the electrode to allow current to travel in two oppositedirections for conducting current uniformly around the portion of thetissue to be severed.

In an embodiment, the elastomeric structure is a suction cup. In afurther embodiment, the device comprises one or more suction elementsconnected to the suction cup for applying suction within the suctioncup. In an embodiment, the suction cup further comprises a flared skirtextending from an edge of the suction cup for securing the suction cupagainst the lens capsule to form a vacuum seal.

In some embodiments, the support structure comprises a series ofopenings along the length of the support structure. In one aspect of theembodiment, the support structure comprises a plurality of tabs. In afurther aspect of the embodiment, the support structure comprises aplurality of tabs so that the portion of the support structure incontact with the elastomeric structure does not form a complete circuitfor current flow.

In certain embodiments, the cutting element is positioned on one side ofthe support structure. In other embodiments, the cutting element ispositioned on at least two sides of the support structure. In oneembodiment, the cutting element comprises at least two electrodes. Inother embodiments, the cutting element is positioned on at least threesides of the support structure.

In an embodiment, the device comprises a stem attached to theelastomeric structure to provide support between a handle and theelastomeric structure and attached structures. In some embodiments, thestem comprises electrically conductive elements for providing current tothe cutting element. In some embodiments, the stem comprises a tube forapplying suction between the elastomeric structure and the lens capsule.In an embodiment, the stem comprises a support arm. In a furtherembodiment, the support arm is electrically conductive, and wherein thesupport arm is electrically connected to the cutting element. In someembodiments, the support arm is tube-shaped to apply suction between theelastomeric structure and the lens capsule.

Also provided herein, in certain embodiments, is a capsulotomy devicefor accessing a lens capsule through a cornea of an eye, the devicecomprising: an elastomeric structure; and a support structure mounted tothe elastomeric structure, the support structure comprising a pluralityof openings along the length of the top of the support structure whereinthe top of the support structure is attached to the elastomericstructure, the support structure comprising a cutting element segmentalong the length of the bottom of the support structure.

In some embodiments, the support structure comprises at least twomaterials, wherein the material comprising the cutting element segmentis more conductive than the material of the support structure attachedto the elastomeric material. In certain embodiments, the supportstructure and the cutting element segment are continuous and made fromthe same material. In an embodiment, the support structure comprises aplurality of tabs attached to the elastomeric structure and wherein thesupport structure connects the elastomeric structure to the cuttingelement segment. In some embodiments, the support structure isdiscontinuous to inhibit current flow around the path of the supportstructure attached to the elastomeric structure.

In some embodiments, the support structure is attached to a support armextending into a stem of the device. In an embodiment, the support armis conductive to allow current to flow along the support arm from thestem to the cutting element segment. In certain embodiments, the supportarm comprises u-shaped elements extending from the support structure,and wherein the u-shaped elements comprise tubes for applying suctionbetween the elastomeric structure and the lens capsule. In oneembodiment, the support arm is tube-shaped for applying suction betweenthe elastomeric structure and the lens capsule.

In one embodiment, provided herein is a method for performing acapsulotomy of a lens capsule of an eye, the method comprising:contacting the lens capsule with a cutting element, wherein the cuttingelement extends from a support structure, wherein the support structureis mounted to an elastomeric structure, and wherein the cutting elementand the elastomeric structure are not in physical contact; and applyingenergy to the lens capsule along the cutting element during theapplication of stress, resulting in the cutting of a portion of the lenscapsule along the cutting element.

In one embodiment, the cutting element is an electrode. In anotherembodiment, the electrode is circular. In an embodiment, the cuttingelement is in uniform contact with the lens capsule.

In some embodiments, applying energy comprises applying an electricpulse or a series of pulses to the electrode. In other embodiments,applying energy comprises applying resistive heating along the cuttingelement.

In certain embodiments, the elastomeric structure is a suction cup. Inan embodiment, the method comprises applying a suction to the suctioncup for securing the suction cup to the lens capsule of the eye afterplacing the cutting element inside the anterior chamber of the eye intoa cutting position on the lens capsule, the suction pulling tissue ofthe lens capsule against the cutting element. In some embodiments, themethod comprises applying a suction to the suction cup, the suctionsecuring a flared skirt of the suction cup against the lens capsule andpulling tissue against the cutting element.

In an embodiment, provided herein is a method for performing acapsulotomy of a lens capsule of an eye, the method comprising:contacting the lens capsule with a cutting element segment, wherein thecutting element segment extends from the bottom of a support structurealong its length, wherein the top of the support structure is mounted toan elastomeric structure, and wherein the length of the top of thesupport structure comprises a plurality of openings to inhibit the flowof current at the top of the support structure attached to theelastomeric structure; and applying energy to the lens capsule along thecutting element during the application of stress, resulting in thecutting of a portion of the lens capsule along the cutting element.

In some embodiments, provided herein is a device for accessing a secondlayer of tissue behind a first layer of tissue for performingmicrosurgery or therapeutic work, the device comprising: an operationalelement associated with the elastomeric structure for engaging inmicrosurgery or therapeutic work on the second layer of tissue, whereinthe operational element is attached to a support structure.

In an embodiment, the operational element comprises a cutting elementmounted to the elastomeric structure for cutting a portion of the secondlayer of tissue. In certain embodiments, the cutting element is anelectrode.

Also provided herein, in some embodiments, is a method for accessing asecond layer of tissue behind a first layer of tissue for performingmicrosurgery or therapeutic work, the method comprising: contacting thesecond layer of tissue with a cutting element, wherein the cuttingelement is mounted to an elastomeric structure, and wherein the cuttingelement is attached to a support structure; and engaging in microsurgeryor therapeutic work on a portion of the second layer of tissue.

In some embodiments, engaging in microsurgery or therapeutic workfurther comprises cutting a portion of the second layer of tissue with acutting element mounted to the elastomeric structure.

These and other embodiments of the invention are further described inthe Figures, Description, Examples and Claims, herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side perspective view of the microsurgery/capsulotomy devicewith the suction cup deployed and in contact with the lens capsule ofthe eye, according to an embodiment of the invention.

FIG. 2 is an expanded cross-sectional view of themicrosurgery/capsulotomy device with a suction cup deployed and incontact with the lens capsule of the eye, according to an embodiment ofthe invention.

FIG. 3A is a schematic cross-sectional view of the capsular membrane incontact with the electrode and skirt of the microsurgery/capsulotomydevice, according to an embodiment of the invention.

FIG. 3B is a schematic cross-sectional view of the capsular membrane incontact with the electrode and skirt of the microsurgery/capsulotomydevice where suction has been applied between the capsular membrane andthe suction cup, according to an embodiment of the invention.

FIG. 3C shows cross-sectional views of electrode positioning along theelectrode support ring according to certain embodiments of theinvention.

FIG. 4 is a side perspective view of the microsurgery/capsulotomy devicewith the suction cup deployed and in contact with the lens capsule ofthe eye, according to an embodiment of the invention.

FIG. 5 is a front perspective view of the microsurgery/capsulotomydevice with the suction cup deployed and in contact with the lenscapsule of the eye, according to an embodiment of the invention.

FIG. 6 is a cross-sectional view of the device showing the relationshipbetween the elastomeric suction cup, electrode support ring, electrode,potting material, and suction cup skirt, according to an embodiment ofthe invention.

FIG. 7 is a partial cross-sectional view of the microsurgery/capsulotomydevice showing the positioning of the suction tube, the leading edge ofthe inserter, the electrical lead wire, the end of the wire, and theelectrode bond pad, according to an embodiment of the invention.

FIG. 8 shows a bottom view of the microsurgery/capsulotomy device,according to an embodiment of the invention.

FIG. 9 shows a top view of the microsurgery/capsulotomy device, showingthe resistive heating device without an elastomeric suction cup,according to an embodiment of the invention.

FIG. 10 shows a top view of the microsurgery/capsulotomy device showingthe outer layer of the stem structure and the components located withinthe stem structure, according to an embodiment of the invention.

FIG. 11 shows the interface between the wires providing current to theelectrode located on the electrode support ring, according to anembodiment of the invention.

FIG. 12 shows an embodiment of the device in which the support arms areplated with an electrically conductive substance and attached to theelectrode support ring and electrode.

FIG. 13 shows another view of an embodiment of the device in which thesupport arms are plated with an electrically conductive substance andattached to the electrode support ring and electrode.

FIG. 14 is a top perspective view of the microsurgery/capsulotomy devicewith the suction cup deployed, according to an embodiment of theinvention.

FIG. 15 shows the conceptual sequence of steps for compression of thesuction cup to fit inside the inserter for entry into the eye, accordingto an embodiment of the invention.

FIG. 16 is a top perspective view of a low friction compression devicewith converging sidewalls, according to an embodiment of the invention.

FIG. 17 shows the compression chamber with the suction cup stored insidea compression chamber, according to an embodiment of the invention.

FIG. 18 shows an expanded view of the suction cup stored inside acompression chamber, according to an embodiment of the invention.

FIG. 19 shows an embodiment of an electrode support ring configured tobe attached to wire leads to provide current to the electrode.

FIG. 20 is an expanded view of the attachment of the wire lead to theelectrode support ring, according to an embodiment of the invention.

FIG. 21 shows an elastomeric structure connected to an electrode via anelectrode support structure, according to an embodiment of theinvention.

FIG. 22 is an expanded view of the interface between an electrode andelectrode support structure comprising tabs, according to an embodimentof the invention.

FIG. 23 shows the interface between the electrode support structure andthe elastomeric structure (e.g., suction cup) via bent tabs locatedwithin the elastomeric structure, according to an embodiment of theinvention.

FIG. 24 is an expanded side view of the interface between the electrodesupport structure and the elastomeric structure (e.g., suction cup) viabent tabs inserted into the elastomeric structure, according to anembodiment of the invention.

FIG. 25 is a top perspective view of another design of the supportstructure and cutting element, according to an embodiment of theinvention

FIG. 26 shows a schematic cross-section of the applied forces in thevicinity of an electrode, according to an embodiment of the invention.

FIG. 27 shows a schematic cross-section with the electrode located onthe bottom surface of the elastic support ring, according to anembodiment of the invention.

FIG. 28 shows an embodiment of the microsurgery/capsulotomy device witha deployed piston for applying suction to the suction cup.

FIG. 29 shows an embodiment of the microsurgery/capsulotomy device witha piston for applying suction to the suction cup where the piston isretracted into the stem of the device.

The figures depict an embodiment of the present invention for purposesof illustration only. One skilled in the art will readily recognize fromthe following description that alternative embodiments of the structuresand methods illustrated herein may be employed without departing fromthe principles of the invention described herein.

DETAILED DESCRIPTION

Embodiments of the invention are described herein in the context of alens capsule surgery in which a portion of the anterior surface of alens capsule is cut. This technique may be used for performing treatmentfor cataracts in which all or a portion of a lens located within thelens capsule is removed from the eye. The procedure may also be used tocreate an access hole in the lens capsule through which to implant anartificial lens (e.g., an intraocular lens, or IOL) within the lenscapsule. Though often described herein in terms of performing lenscapsule surgery, the devices and procedures are not limited to lenscapsule surgery, but can also be useful in other treatments of the eye,such as a corneal surgery, treatments for glaucoma, microfenestration ofthe optic nerve, surgeries involving decemet's membrane, among others.Furthermore, the devices and procedures may also be useful in thedelivery of pharmacologic, biologic, and chemical entities andtherapeutics. The devices and procedures can also be used to deliverfluids in addition to suction, and the delivery can be specificallylocalized (e.g., by the suction cup) limiting exposure only to desiredtissues. In addition, the devices and procedures may be useful forindustrial applications or performing other medical procedures outsideof the eye, such as procedures involving excision of delicate membranesor tissue structures, fenestration of brain dura, vascular tissues andothers. The devices and procedures can also be used outside of the body,on tissue excised and separate from the body, for industrialapplications, etc. In these other types of applications, the proceduresand devices function generally in the same manner as described regardingthe lens capsule surgery, though the components may be differentlyarranged, sized, shaped to accommodate different tissue.

The term “pulse” as used herein refers to the length of time theelectrical pulse is on, for example 100 microseconds. If the pulse is aDC pulse the current is going in only one direction (but amplitude maybe changing) during the entire 100 microseconds. If it is an AC pulsethe current reverses direction during the 100 microseconds. If the ACfrequency is in the RF or in the microwave range there will be manycycles during the 100 microsecond pulse. The frequency and amplitude maychange or slow during the 100 microseconds and that kind of pulse iscalled a “chirp”), and the current path may go around the ring of metal,or may go from the ring through tissue to a return electrode.

The term “elastomeric structure” refers to a bendable/foldable structurethat can provide an air-tight seal between the edges of the elastomericstructure and tissue. In one embodiment, the elastomeric structure isfunctionally linked to a cutting element, the elastomeric structureproviding a fluidic seal between the elastomeric structure and thetissue, allowing a vacuum pressure applied between the elastomericstructure and the tissue to result in a pressure that presses thecutting element against the tissue.

The term “cutting element” refers to an element designed to cut tissuethrough application of pressure and/or electrical current. The cuttingelement can be made from various materials. In one embodiment, thecutting element refers to an “electrode” (e.g., an “electrode segment”).The metallic components of the electrode can be made by electroformingof suitable metals such as nickel, gold, steel, copper, platinum,iridium, etc. Connections between the electrode and leads in the stemcan be made by electroplating, or welding. Typically, for electricalcutting elements, the material for the cutting element is electricallyconductive, and for mechanical cutting elements, the material is hardenough to pierce the membrane. For both electrical and mechanicalcutting elements, the material is also generally elastic enough toreturn to its prior shape after being squeezed to get through the tissueincision, or soft enough to be pushed back into circular shape by thepolymeric support ring and/or by the suction cup in which it is mounted.For example, for an electrical cutting element, the materials caninclude those made by photochemical etching, such as spring steel,stainless steel, titanium nickel alloy, graphite, nitinol (NiTi alloy“memory metal”), nickel, nickel-chrome alloy, tungsten, molybdenum, orany other material that will allow the element to return to its priorshape. Other materials for electrical cutting elements includeelectrically conductive elastomers, including elastomers (e.g., siliconeor polyurethane) mixed with appropriately shaped conductive particles(e.g., silver, gold, graphite, or copper) that can establish contactwith each other and continue to be in contact with each other for theduration of the electrical discharge. An additional example of amaterial for electrical cutting elements includes a compliant mesh ofvery fine wires (e.g., diameter of about 1 or 2 microns) that can beanchored in the elastomeric support ring to make the conductive element.As a further example, materials can be used for electrical cuttingelements that are made by sputtering metal onto a polymeric support,such as high conductivity metals (e.g., gold, aluminum, copper, etc.),which can be used to make very thin (e.g., 1 micron) elements withresistance within the usable range (e.g., 1 to 10 ohms) deposited by RFplasma sputtering.

Materials used for mechanical cutting elements can includephotochemically etched metal (e.g., stainless steel), or a relativelyhard plastic (e.g., phenolic), among others. Discrete micro teeth couldbe etched from single crystal silicon. Photochemical etching can used tomake cutting elements that have a thickness of, for example, 25 microns,or 12.5 microns, or 5 microns, and so forth.

The term “conductor” refers to a substance or medium that conducts anelectric charge. Whenever “gold” is mentioned herein as an element usedas a conductor, it is to be understood that alternative materialssuitable as good conductors may also be used, including by way ofexample and not limitation, Pt, Cu, Ni, Ta, Ir, Re, and their alloys. Aconductor may refer to a heating element. Heating elements may be madefrom a large set of suitable conductive materials, including by way ofexample and not limitation: gold, Pt, Ta, Ir, Re, Al, Ag, and theiralloys (e.g., Ta/Al, Pt/Ir, etc.), tantalum nitride, titanium nitride,carbides that are doped to be conductive, etc.

The term “insulator” refers to any material or object that does noteasily allow heat or electricity to pass through it, e.g., a materialwith a very low electrical conductivity or thermal conductivity orsomething made of such a material. An insulator may include, by way ofexample and not limitation, polymers (e.g., kapton, silicone, etc.),glass (e.g., chemically strengthened glass), ceramics (e.g., tantalumoxide, titanium oxide, nonconductive oxides, nitrides, and oxynitrides,etc.).

The term “cutting element support structure,” “electrode supportstructure,” or “support structure” refers to a structure used to extendfrom and/or attach to and support a cutting element or electrode. Insome embodiments, the electrode support structure is elastomeric. Insome embodiments, the support structure is made of nitinol. Whenevernitinol is mentioned as a material used for mechanical support elementsuch as an electrode support structure, it is to be understood that anysuitable elastic material may be substituted, by way of example and notlimitation: chemically strengthened glass, Hi Ten steel, stainlesssteel, polymer, Kapton, etc. In some embodiments, the electrode supportcomprises a series of tabs that provide an interface between theelectrode and another structure, e.g., potting material or anelastomeric structure (e.g., a suction cup). In some embodiments, thecutting element support structure is mechanically separate from, butattached to, the cutting element. In other embodiments, the cuttingelement support structure is an extension of the cutting element, e.g.,an extension of a conductive electrode, wherein the electrode supportstructure segment is less conductive and extends from the supportstructure. In other embodiments, the cutting element support structureis an extension of the cutting element made from the same material aseach other, and wherein the cutting element support structure hasnotches to prevent flow of current around the cutting element supportstructure.

Microsurgery/Capsulotomy Device

A problem solved by this invention is how to perform a manualcapsulotomy without inadvertently tearing tissue outside of the desiredcircular path. Using the present invention, the tear will follow thelocation of the thermally weakened material, which is defined by anelectrode (e.g., a circular electrode). The tear will not run off intothe stronger cold material. In one embodiment, the invention controlsboth the stresses in the membrane and the strength of the membrane atthe exact circular path of interest, so undesired processes cannotoccur.

In one embodiment, the microsurgery/capsulotomy device described hereinuses suction force to contact a capsular membrane with the edge of acircular metal electrode, thereby establishing a state of uniform,circular contact between the electrode and the lens capsule, exactlywhere cutting is desired on the membrane, e.g., a circle on the capsularmembrane. A short burst of electrical energy may then be passed throughthe electrode to cause stress along the electrode's contact with themembrane and complete the cut of the membrane along the electrode. Theduration of the electrical pulse is less than 10 milliseconds(preferably about 10 to 100 microseconds or less) so that only a smallvolume of tissue is heated by it. The nature of the pulse may be DC, orAC (radio waves e.g., 1 MHz, or microwaves e.g., 2.4 GHz).

In another embodiment, a circular metal electrode, without suction cup,is carefully placed into uniform circular contact with the lens capsuleto effect cutting in the same manner.

In one embodiment, described herein is a microsurgery/capsulotomy devicecomprising a circular electrode supported by a mechanically elasticelectrode support structure. The electrode is made from a conductivemetal, e.g., by way of example and not limitation: gold, platinum,copper, nickel, tantalum, iridium, rhenium, and their alloys. Themechanically elastic electrode support structure is made from an elasticmaterial, e.g., by way of example and not limitation: nitinol (e.g.,superelastic nitinol), chemically strengthened glass, Hi Ten steel,stainless steel, polymer, Kapton, etc. In this embodiment, where themechanically elastic electrode support structure is made from an elasticmaterial, it may be deformed to allow the microsurgery/capsulotomydevice to be inserted through a small corneal incision, and thenexpanded back to its original shape within the anterior chamber of theeye. In one embodiment, the microsurgery/capsulotomy device furthercomprises an elastomeric structure (e.g., a suction cup), which attachesto the lens capsule. A suction force then will pull the capsularmembrane in close contact with the electrode, where an electricalcurrent lasting less than 0.0005 seconds (and preferably less than0.0001 seconds) results in cutting the membrane. In some embodiments,the excised circular patch may be sucked out by a suction tube of thedevice. In other embodiments, the excised circular patch may be removedfrom the eye by sticking to the roof of the suction cup. Theseembodiments are described in more detail below.

In several embodiments of the invention, high temperatures generatedfrom the current traveling to and through the electrode do not reach theelastomeric structure. This prevents outgassing caused by the heating ofthe device. In one embodiment, this is accomplished by placing a highconductivity circuit as a separate cutting element directly onto acutting element support structure. The current will preferentially flowin through the cutting element and the support structure will notgenerate a lot of heat. Thus, the elastomeric structure will not reach ahigh temperature. In another embodiment, an insulating layer (i.e., aninsulator) is placed between the support structure and the cuttingelement. In this case, the cutting element may be the same material or adifferent material than the support structure. In another embodiment,the support structure provides both a supporting function and its edgeprovides the cutting function (i.e., one structure serves bothfunctions). In one aspect of this embodiment, the top portion of thesupport structure (where it is in contact with the elastomericstructure) has cutouts that prevent the current from flowing in acircuit around the top of the support structure. The bottom of thesupport structure has no cutouts, and thus can act as a cutting element(e.g., an electrode) with current flowing in a continuous path aroundthe cutting element and generating the necessary heating for capsulecutting. In this case, a cutout is any modification to the supportstructure that inhibits current flow around the portion of the supportstructure attached to the elastomeric structure. These cutouts mayresult in ‘tabs’ that can be pointed radially into the center of theelastomeric structure, or remain aligned circumferentially.

FIG. 1 is a side perspective view of the microsurgery/capsulotomy device1 in use in the eye. The relevant parts of the eye shown are the cornea6 and the surface of the lens capsule 7. In the device, there is anelastomeric suction cup 2 that is held by suction force onto the lenscapsule. The suction cup is attached to a stem 4 that contains tubingfor suction, and electrical conductors for electrical currents. Withinthe suction cup is an electrode that confronts the capsule. The deviceis slid through an inserter 3 that has been pushed through a previouslymade incision 5 in the cornea.

Steps in a method of using the microsurgery capsulotomy device accordingto an embodiment of the invention are described below:

-   1. Visco (or other lubricating material) is applied to the suction    cup 2 to act as a lubricant.-   2. The suction cup and electrode are compressed (in a compression    tool) to fit within the inserter (note that FIG. 1 does not show the    handpiece structure (described later) to which the inserter is    attached and through which the stem slides).-   3. The suction cup and electrode are slid into the inserter.-   4. A corneal incision 5 is made (using a separate ophthalmic tool).-   5. The inserter 3 is pushed through the corneal incision.-   6. The suction cup, electrode, and stem are made to slide out of the    inserter to enter the eye.-   7. After the suction cup enters the anterior chamber of the eye, it    returns to its circular shape.-   8. The surgeon positions the center of the circular electrode over    the optic axis of the eye.-   9. Suction is applied.-   10. Suction forces the suction cup and electrode against the lens    capsule.-   11. An electrical current is made to flow through the electrode to    cut the capsule.-   12. The suction is turned off-   13. Optionally, there is a reverse flow of fluid injected between    the suction cup and the lens capsule to break the grip of the    suction cup.-   14. The device and the excised patch of membrane are removed from    the eye.

Note that after steps 1, 2, 3, 5, 6, 7, 8, and 9 the system controllermay send a small test current through the electrode to measure itsresistance. If the resistance is too low or too high, the system willalert the surgeon that the device is broken and needs to be replaced.The measurement of resistance can be made continuously if desired. Thesteps described above are just one example of such a method, but feweror more steps could be used, the steps modified, or the steps spaced outin time, or the steps can be reordered, as desired (the same is true forother methods/listings of steps described in this application).

FIG. 2 shows a cross section of the device in use. The electrode 9(e.g., cutting element) is in contact with the capsule 7, which enclosesthe lens 10. The electrode 9 is supported by an elastically deformablering 12 (e.g., support structure). The suction cup 2 (e.g., elastomericstructure) has a “skirt” or “lip” 8 to facilitate the formation of afluidic seal with the capsule when suction begins. Fluid flow throughtube 11 controls the suction force.

FIG. 3A shows a schematic cross section of the capsular membrane 7forced by suction into contact with the electrode 9 (e.g., 9B, 9-OD(FIG. 3B), or 9-ID (FIG. 3B), and any combination thereof) and the skirt8 of the suction cup 2. The electrode is mechanically supported by theelastically deformable ring 12, which is held to the suction cup bypotting material 14. Electrical lead 13 brings electrical current to theelectrode. In some embodiments, the electrode 9 is placed along thebottom of the support structure 9B, the inner diameter of the supportstructure 9-ID (FIG. 3B), along the outer diameter of the supportstructure 9-OD (FIG. 3B), or any combinations thereof. Some embodimentsof this configuration are shown in more detail in FIG. 3C, as describedbelow.

FIG. 3B shows a modification of FIG. 3A where the suction has beenincreased to pull the capsule 7 into contact with the electrode 9 (e.g.,9B, 9-OD, or 9-ID, and any combination thereof) and the skirt 8 of thesuction cup 2. The electrode is mechanically supported by theelastically deformable ring 12, which is held to the suction cup bypotting material 14. Electrical lead 13 brings electrical current to theelectrode.

FIG. 3C shows cross sectional views of seven locations where electrodes(e.g., gold) are plated on the bottom of the elastic support ring incertain embodiments of the invention. In some embodiments, the elasticsupport ring is made from superelastic nitinol. Each design results in adifferent magnitude and distribution of tensile and shear stresses inthe membrane when suction is applied, and a different distribution ofheat flow and resulting temperatures after the electrical dischargeoccurs. In one embodiment, the electrodes are configured differently forpeople whose capsules tear cleanly in shear (e.g., older adults) vs.designing electrodes for people whose capsules need high tensile stressto tear (e.g., younger adults and children), as discussed later in thisapplication. FIG. 3C-A shows the electrode along the bottom of thesupport ring, according to an embodiment of the invention. FIG. 3C-Bshows the electrode on the inner dimension of the bottom of the supportring, according to an embodiment of the invention. FIG. 3C-C shows theelectrode on the outer dimension of the bottom of the support ring,according to an embodiment of the invention. FIG. 3C-D shows theelectrode on the bottom and the inner dimension of the bottom of thesupport ring, according to an embodiment of the invention. FIG. 3C-Eshows the electrode on the bottom and the outer dimension of the bottomof the support ring, according to an embodiment of the invention. FIG.3C-F shows the electrode on the inner dimension and the outer dimensionof the bottom of the support ring, according to an embodiment of theinvention. FIG. 3C-G shows the electrode along the bottom, the innerdimension, and the outer dimension of the bottom of the support ring,according to an embodiment of the invention. These are just someexamples of electrode designs, but the electrode can be otherwisepositioned as desired. Different surface textures will trap differentamounts of liquid (e.g., a viscoelastic or suitable lubricant) betweenthe membrane and the electrode. A smooth surface along the electrodewill maximize heat conduction from the electrode directly to themembrane. The various electrode designs illustrated in FIG. 3C can beused with any of the devices described in this application.

FIG. 4 shows a side view of the device 1 in use in the cornea andresting on the capsular membrane of the lens. FIG. 5 shows a front viewof the device 1. FIG. 6 shows a sectional view of the device with theelastomeric suction cup 2, electrode ring support 12, electrode 9 (9B,9-ID), potting material 14, and suction cup skirt 8. In one embodiment,the electrode ring support 12 is nonconductive or less conductive thanthe electrode 9 to prevent heating of the suction cup 2. In anotherembodiment, slots or one or more other discontinuities are introducedinto the top of the electrode support ring 12 to prevent current flowaround the top of the electrode support ring, and thus prevent heatingof the suction cup 2. In one embodiment, the electrode support ringcomprising slots is of the same material as the electrode. In anotherembodiment, the electrode and electrode support ring are part of acontinuous structure, with the electrode defined as the part that allowscurrent flow and contacts the capsular membrane of the lens or othertissue to induce a tear along the electrode. The portion of thestructure serving as the electrode support ring does not allow currentflow and is in contact with the elastomeric structure. This embodimentalso avoids heating of the suction cup. FIG. 7 shows a frontcross-sectional view of the device showing the suction tube 11, theleading edge 20 of the inserter 3, the insulated electrical lead wire17, and the end 16 of the wire 17 that is bonded to an electrode bondpad 26 (see FIG. 8).

FIG. 8 shows a bottom view in which can be seen an electrode bond pad26, and a connecting trace 29 from the bond pad to the electrode. Thesupport ring 12 has openings or holes 19 which allow the pottingmaterial 14 to lock the ring into place, or where there is no pottingmaterial, to let fluid flow occur to establish suction. The holes 19also help to avoid kinking in the electrode when expanding from acompressed state. The suction cup has an elastomeric neck region 21 thatconnects to the stem. During use, the suction force will deform thesuction cup and pull the surface 18 into contact with the lens capsule.In some embodiments of the present invention, means are provided to makethe capsule stick to surface 18 sufficiently well that the excisedcircular patch of membrane is carried out of the eye with the devicewhen it is withdrawn. This sticking force may be provided, in someembodiments, by chemical groups that stick to collagen of the membrane,or by micromechanical sharp points, or by a combination of sharp pointscoated with sticky chemicals. In one embodiment, a small point of stickymaterial (e.g., partially cured silicone gel) is applied to center ofroof. In another embodiment, a small patch of roof 18 is coated withsticky material (e.g., silicone gel). This sticky patch is coated with asoluble non-sticky layer (e.g., polyvinyl alcohol, PVA) to preventself-adhesion during compression of the patch to enter the eye. Afterless than about one minute in the eye the PVA will diffuse away, and theviscoelastic solution will flow out of the interface sufficiently (dueto suction pressure) for the sticky coating to contact the membrane. Incertain embodiments, the texture of the roof 18 will have hills andvalleys molded into it to allow fluid to flow out of the interface andnot get trapped. This allows the surface 18 to contact the membraneenough to stick to it and remove the excised patch out of the eye.

Another mechanism to contribute towards the retention and removal of theexcised patch is a localized vacuum line that touches the patch. Thiscan be a separate line from the main suction line so that it can stillapply a vacuum to the patch during the step when the main suction lineis supplying material back to the suction cup to break its grip on thelens. Another mechanism to contribute towards the retention and removalof the excised patch is micromechanical sharp points located along andwithin the suction line.

FIG. 9 shows the device as it would appear without the suction cup orpotting material in the way. An elastically deformable support arm 24 isbonded (e.g., by spot welding) to the elastically deformable ring 12over the region 23. In one embodiment, the elastically deformable ring12 and the support arms 24 are made from superelastic nitinol and thesupport arms 24 are bonded to the elastically deformable ring 12 bywelding (laser welding, or electrical resistance spot welding). Thenitinol members may be cut (e.g., by laser) from strips of foil, and mayundergo the shape setting process prior to welding. The support arms areattached to stem block 22, which also anchors the insulated wires 17 andthe suction tube 11 within the lumen of the stem (not shown). The stemblock 22 has a structure that mechanically locks it to glue or pottingmaterial (e.g., silicone or polyurethane) that bonds to the neck 21 ofthe suction cup (silicone cup to stick to silicone potting, orpolyurethane cup to stick to polyurethane potting).

FIG. 10 is similar to FIG. 9, but the inserter has been removed and theouter layer 25 of the stem structure can be seen. In one embodiment thisouter layer is comprised of heat shrink tubing (e.g., polyester lessthan about 0.1 mm in thickness).

In FIG. 11 (oriented with the bottom surface facing up) can be seen theelectrode 9 (9-ID), electrical connecting path 29, bond pad 26, bondedwire end 16, the optional weld 28 (may be present if the ring is madefrom an initially flat foil), thru hole 19 allowing fluid flow forsuction, and thru holes 31 to provide locking engagement with pottingmaterial. The dimensions of the thru holes 31 and 19 allow forfine-tuning of the stiffness of the elastic ring for a given availablethickness of foil or sheet stock. The stiffness must be high enough toensure that the ring can return to its circular shape inside theanterior chamber, but it should be as low as possible to minimizefriction forces for sliding inside the inserter 3.

In some embodiments of the invention, the electric current flows in onelead, and to the electrode via connecting path 29. Then, half thecurrent flows clockwise through one half of the circular electrode, andthe other half of the current flows counterclockwise though the otherhalf of the circular electrode, to the other lead (180 degrees from thefirst lead) via another connecting path (not shown) to ground. In oneembodiment, the source of the electrical current is a capacitor that hasbeen charged to a predetermined voltage.

In this section, we describe an embodiment of the device to thermallyisolate the heated electrode from the elastomeric suction cup to avoidthe possibility of outgassing. The electrode may reach a temperature of1000° C. (or within the range of 500° C. to 1300° C.) for 0.0001 second(or within the range of 0.00001 sec to 0.001 sec). In one embodiment ofthe present invention, a good electrical conductor, such as gold, isused to form the electrode. Other materials such as copper, silver,graphite, graphene, carbon nanotubes, etc., may also be used as anelectrical conductor. In one embodiment, the supporting ring issuperelastic nitinol. If the gold is plated directly on bare nitinolmetal, good adhesion can be achieved so it will not come off in use.Part of the electrical current will go through the gold, and part willgo through the nitinol. The fraction of current that goes through eachpath depends on the resistance of the path. Gold is about 34 times moreconductive than nitinol in the austenitic phase (and about 33 times moreconductive than the martensitic phase). The superelastic nitinol free ofapplied stress is austenitic above about 8° C., and only forms themartinsite phase where stress exceeds a certain threshold during thedeformation to get through the corneal incision. Since the powerdissipated through a resistor is P=I²R, in one embodiment, we maximizethe current in the smallest possible volume to maximize the powerdensity so the power density will be high in the gold and low in thenitinol. Also the specific heat of gold is about ⅓ that of nitinol. Forthe same energy dissipated in the same mass of material the temperaturerise in the nitinol will only be ⅓ as much as the gold. Thus, in oneembodiment, the mechanical connection to the elastomer is made throughnitinol. In this embodiment, the maximum temperature that reaches theelastomer will be kept below a value at which outgassing would become aconcern.

In one embodiment of the invention, the dimensions of the elastic ring12 and electrode are as follows: Nitinol ring—Outer diameter: 5.5 mm,inner diameter: 5.45 mm, height 0.4 mm. Plated gold—thickness: about0.01 mm or less, width: 0.1 mm, areas to plate: (1) Inner diameter edge,(2) outer diameter edge (3) bottom edge, (4) any combination of these(see, e.g., FIG. 3B, and FIG. 3C Embodiments A-G).

In some embodiments, the nitinol is covered by an electricallyinsulating layer prior to gold plating. In one embodiment, a method tocover nitinol with an electrically insulating layer prior to goldplating is as follows:

-   1. Laser cut nitinol parts from foil.-   2. Electropolish the nitinol parts.-   3. “Set-shape” the nitinol ring and support arms (in their    respective fixtures at about 500° C. for about 10 minutes, then    quench the components in water).-   4. Weld (e.g., laser, tig, or resistance welding) ring edges 28    together (optional).-   5. Optionally weld nitinol support arms to ring.-   6. Grow thermal oxide in controlled atmosphere furnace.-   7. Set nitinol structure in shadow mask.-   8. Sputter adhesion layer (e.g., 250 Angstroms to 1000 Angstroms    Ti).-   9. Sputter seed layer (e.g., 250 Angstroms to 1000 Angstroms Au (or    Ni)).-   10. Remove from shadow mask.-   11. Plate gold (for example 10 microns thick).

The device generated by the method above will inhibit flow of currentthrough the nitinol during use of the device (because of the insulatinglayer). This will decrease the temperature rise seen by the elastomericstructure, and the device will be more efficient. Although gold maystill be used as a conductor, other conductors having lower conductivitymay be used as the functioning of the device no longer depends on theratio of conductivities of the electrode material to the nitinol ring.Thus, in some embodiments, a higher melting point material such asnickel, stainless steel, or superelastic nitinol, may be used asmaterial for the heated electrode. These materials have higherresistivity, so a higher voltage discharge will be needed to get thesame power in the same short duration pulse as achieved in gold. In apreferred embodiment, the insulating layer (e.g., oxide or nitride) willbe thick enough to prevent significant electron transport from theelectrode to the elastic support ring during the discharge for thechosen applied voltage.

Many techniques are known in the art to accomplish the goal of attachinga gold electrode to a supporting superelastic nitinol ring. With thenitinol as a flat sheet, photolithography may be performed to mask whereplating is not desired. In another technique, after shape setting andwelding, photolithography may be performed on the cylindrical surfaceprior to gold plating.

FIGS. 12 and 13 show an embodiment of the device in which the nitinolsupport arms 30 have been plated with gold to serve as the electricalleads to the electrode. This allows the removal of the wires 17 from thesuction cup and stem. In one embodiment, the cross-sectional area of thegold on the support arms is much greater than that of the electrode, sothe support arms do not get hot in use. Thru holes in the nitinol ringallow thru plating of the gold such that gold to gold bonding (orsoldering) can be used to make the mechanical connection of the supportarm to the electrode support ring, and the electrical connection of theelectrically conductive support arm to the electrode. Any of the devicesdescribed herein could be modified to include this design includingconductive support arms. In one embodiment, the support arm is modifiedto comprise a channel or tube for applying suction (e.g., the supportarms are provided in the shape of u-shaped channels to form a tube forapplying suction (see, e.g., FIG. 25)).

FIG. 14 shows an overview of the device mounted on a handpiece,according to an embodiment of the invention. There are two assemblies:the outer housing, and the inner unit that slides relative to the outerhousing. The outer housing is comprised of sleeve 50, nosepiece 53, andinserter 3. The inner unit is comprised of tubing to conduct suction 56,electrical conductors 55, thumb slide 52, and stem 57. To move thesliding unit, the surgeon pushes the thumb slide 52 along guide slot 51.A side channel 54 on each side of the sleeve 50 engages the latchingarms 61 (see FIG. 17) of the compression chamber 60 (see FIGS. 17, 18).

FIG. 15 shows, according to an embodiment of the invention, a sequenceof steps in deploying the device through a corneal incision:

-   1. As packaged, the suction cup 2 is located between compression    beams 58 in the compression chamber 60 (Step A).-   2. The user pushes the compression beams together so the suction cup    is narrower than the inserter lumen width (Step B).-   3. The suction cup is pulled into the inserter (Step C).-   4. The compression chamber is unlatched from the handpiece and    discarded (Step D).-   5. The inserter is inserted into the corneal incision, and the    suction cup is pushed out of the inserter (Step E).

FIG. 16 shows the sequence of steps in deploying the device using afunnel-like passive compression structure 59. The suction cup undergoescompression as the user moves the thumb slide 52 away from thecompression chamber. In this embodiment, converging sidewalls 59gradually compress the suction cup 2 as it is pulled into the inserter3. In one embodiment, friction is low because the compression chamber isflooded with saline, or viscoelastic, or other lubricants, prior to use.The floor and roof of the compression chamber physically constrain thesuction cup or electrode, and prevent the suction cup or electrode fromdeflecting out of plane, shown in Step A. Without the shaped convergingsidewalls, all of the work of compression would have to occur at theentrance to the inserter and the required force would be greater. InStep B, the suction cup is fully inside the inserter. In Step C, thecompression chamber has been removed. In Step D, shows the device as itwould appear after the inserter has been pushed through the cornealincision and the suction cup deployed within the anterior chamber. Inone embodiment, the low friction compression device is used for a devicecomprising an electrode ring and electrodes alone without a suction cup.

FIG. 17 shows a plan view of a compression chamber 100 latched on to ahandpiece sleeve 50 by means of latching arms 61, according to anembodiment of the invention. As packaged, the suction cup 2 is not understress, and is located within the compression chamber, which willconstrain it from vertical deflection when the compression beams 58 aremoved toward each other to compress the suction cup.

FIG. 18 shows a passive compression chamber having a 2-dimensionalfunnel-like shape with converging walls 62 which compress the suctioncup 2 as it is slid out of the chamber and into the inserter, accordingto an embodiment of the invention. Any of the devices described hereincould be used with the handpiece and methods of FIGS. 14-18.

FIG. 19 shows an elastic ring 64 made of, e.g., nitinol, or stainlesssteel. In one embodiment, the elastic ring 64 is made of stainless steeland the elastic ring will be of sufficient dimensions (e.g., a wallthickness of about 0.01 mm, up to about 0.025 mm) to avoid permanentplastic deformation during the deflection needed to insert it into theeye. In another embodiment, the elastic ring 64 is made fromsuperelastic nitinol. In this case, the ring may be thicker (e.g., awall thickness of about 0.05 mm up to about 0.075 mm). FIG. 19 shows anembodiment comprising wire leads 65 attached to the ring. Thisembodiment allows electrodes to float with less stiffness since thesupport arms are wires, allowing the device to have increased pitch androll range of movement. This embodiment may be used with or without theelastomeric structure (e.g., a suction cup). In one embodiment, the wireleads are made of nickel-plated copper or aluminum. In some embodiments,the wire leads are attached via welding, soldering, or brazing. In someembodiments, the wire leads are attached to the outer dimension of theelectrode. According to an embodiment of the invention, a gold electrodeis plated on the bottom surface of the support ring.

FIG. 20 shows an expanded view of the attachment of the wire lead to theelectrode support ring, according to an embodiment of the invention.Holes or openings in the support ring 66 allow for suction flow and/orlocking into the suction cup by potting material, and also help to avoidkinking in the electrode when expanding from a compressed state. In thisdesign, the current will flow from the lead into the ring. It will thenflow through both the gold electrode and the elastic ring. Because goldis about 34 times more conductive than nitinol or stainless steel, thecurrent density in the gold will be 34 times greater than in the ring.Since Power=I²R (where I is current, and R is resistance), the powerdensity in the gold is much greater than in the ring, so the gold willheat up enough to cut the capsule membrane, while the ring will not heatup enough to cause outgassing of the elastomer (e.g., silicone, orpolyurethane) to become a concern. Any of the devices described hereincould include the design of FIGS. 19 and 20.

FIGS. 21-24 show an embodiment of the invention in which the elasticsupport for the electrode isolates the elastomeric structure (e.g., asuction cup) from current running through the electrode by havingdiscrete tabs 75. In one embodiment, these discrete tabs act as theelectrode support structure. The tabs decrease the heat flow to theelastomeric structure by preventing current leakage from the electrode.In one embodiment, the support structure and electrode are continuous,with tabs cut out of the top portion connected to the elastomericstructure, preventing current from flowing in a circuit around the topof the support structure. The bottom of the support structure has nocutouts, and thus can act as a cutting element (e.g., an electrode) withcurrent flowing in a continuous path around the cutting element andgenerating the necessary heating for capsule cutting. In this case, acutout is any modification to the support structure that inhibitscurrent flow around the portion of the support structure attached to theelastomeric structure. These cutouts may result in ‘tabs’ that can bepointed radially into the center of the elastomeric structure (as shownin FIGS. 21-24), or can be aligned circumferentially (e.g., pointing ina direction that generally follows the circumference of the elastomericstructure, see FIG. 25 as an example), or can be otherwise positioned.These tabs can also be shorter or longer than those shown in FIGS. 21-24(e.g., the portion of the tab extending into the elastomeric structurecould be shortened). FIG. 21 shows an elastomeric structure 70, having acompliant sealing skirt 73, and a neck with a lumen 71. The goldelectrode 74 and gold lead 76 are supported by the superelastic nitinolstructure, which is potted in the elastomeric structure. Gold platingmay be applied to the inner dimension 82, and/or bottom 81, and/or outerdimension 80 surfaces as needed (FIG. 22). In one embodiment, thesurface 72 adheres to the excised membrane patch so that it will beremoved from the eye along with the device.

In one embodiment, the electrode comprises vertical members. Thenarrowness of these vertical members prevents heat conduction fromtraveling up the electrode support structure comprised of several tabs75 (FIG. 22). The attachment of this electrode to the suction cup isshown in FIG. 23, according to an embodiment of the invention. In someembodiments, a complete circuit is only present on the bottom of theelectrode support structure around the electrode, preventing electronsfrom flowing up the support structure into the elastomeric structure(e.g., the suction cup). In one embodiment, the tabs 75 are essentiallyrigid compared to the silicone. In some embodiments, the tabs are madefrom stainless steel or superelastic nitinol.

FIG. 25 is a top perspective view of another design of the supportstructure and cutting element 400, according to an embodiment of theinvention. In use, current can flow from rigid lead 401 throughconnecting lead 402 and into electrode ring 403. The current can proceedaround electrode ring 403 (i.e., the cutting element), throughconnecting lead 405 to rigid lead 406. Optional ligament 407 is designedto vaporize at the beginning of the pulse, so that it will not bepresent to conduct current during the remainder of the pulse. Anchoringtabs 404 are also shown in FIG. 25. In one embodiment, the cuttingelement is a circular cutting element mounted to the underside of thesuction cup with the anchoring tabs 404 (i.e., the support structure).In some embodiments, the tabs may have different shapes to attach to thesuction cup, for example bent tabs 75 as shown in FIG. 22. In thisembodiment, the support structure provides both a supporting functionand its edge provides the cutting function (i.e., one structure servesboth functions). The top portion of the support structure (where it isin contact with the elastomeric structure) has cutouts that prevent thecurrent from flowing in a circuit around the top of the supportstructure. The bottom of the support structure has no cutouts, and thuscan act as a cutting element (e.g., an electrode) with current flowingin a continuous path around the cutting element and generating thenecessary heating for capsule cutting. In this case, a cutout is anymodification to the support structure that inhibits current flow aroundthe portion of the support structure attached to the elastomericstructure. These cutouts may result in ‘tabs’ that can be pointedradially into the center of the elastomeric structure (e.g., FIGS.21-24), or can be aligned circumferentially (e.g., FIG. 25). In certainembodiments, the cutting element can take other shapes (e.g.,elliptical, square, rectangular, irregular, and other shapes) fordifferent types of surgical procedures where a differently shapedincision in the tissue is desired. Similarly, the suction cup can takeon other shapes, as well.

Cutting Mechanism

Cutting of the capsular membrane is thought to occur as follows. Thesuction force stretches the membrane over the electrode. This puts themembrane in tension exactly on the circle where cutting is desired. Theapplied forces are acting to pull the material inside the circle awayfrom the adjoining material outside the circle, but the membrane is toostrong to break from this force alone. When the electrical dischargeheats up the electrode, heat starts to flow into the membrane, water,and visco that may be trapped between the electrode and membrane. As thetemperature of the region of the membrane close to the electrodeincreases, the membrane material loses its mechanical strength. Themembrane is held together by hydrogen bonds, Van der Waals forces,mechanically intertwined molecular chains, and covalent bonds. As thetemperature increases the bonds break in order of increasing strength:Van der Waals, hydrogen bonds, mechanical entanglement, then covalentbonds. Even before covalent bonds break, the heated region isapproaching a state of being locally melted, and if the number ofcovalent bonds holding the membrane intact is low, the tensile and shearstresses may be high enough to break the membrane. At the same time,water in the region is becoming heated above the boiling point so thepressure within the membrane is increasing. The weakening of themembrane, the local high expansive pressure from steam within themembrane, and the far field applied tensile and shear stresses are allacting to break the membrane on the circle defined by the electrode.Additional pressure is applied by any steam or expanding visco that istrapped between the membrane and the electrode. After the membranebreaks, the “melted” edges will re-solidify as new hydrogen bonds areformed on cool down. This will make the new edge smooth and free fromstress concentrating defects. In one embodiment, the fast cuttingmechanism of the microsurgery/capsulotomy device works well due to itsspeed. It allows cutting to take place before the heat from the energydischarge has diffused more than about 25 microns, confining the energyused for the cut within the volume of membrane where bond breaking isneeded. After cutting is complete, the heat diffuses away in threedimensions, however, the heat is only about 0.1 joules, so grosstemperature rise of the tissue does occur. There is not enough time orenergy for material diffusion or coagulation of large molecules tooccur.

The fact that the adult capsule tears in shear as neatly as it does,shows that there is little or no covalent cross-linking betweenmolecules in-plane. Molecules can slide past each other vertically, andwith this type of bonding increased temperature weakens it so it willtear at lower applied stress. Pediatric capsules are tougher so they mayhave more in-plane cross-linking, and this may require a differentdesign for the electrode. Looking at the electrode designs in FIG. 3C,different distributions of shear and tensile stress can be achieved, andthe magnitudes of particular stresses can be controlled by the suctionpressure, and the energy and duration of the electrical discharge. Notethat as the mechanical suction force is increased, the thermal energycomponent can be decreased. It will not be necessary to generate steamexpansion if the suction force alone is great enough to make themolecules slide past each other in the microscopic melt zone. Therefore,the maximum temperature of the electrode may be reduced.

As currently practiced, the cataract operation is done with the anteriorchamber filled with “viscoelastic material”. A viscoelastic material isone that behaves as an elastic solid on short time scales, and flows asa viscous liquid on long time scales. Therefore the suction force may begreatly increased if it was timed as a short pulse to coincide with theelectrical discharge. The mechanical motion of the capsule membrane atthe electrode can be small (e.g., 0.005 mm to 0.05 mm). Suction force islimited by cavitation, but cavitation takes time to develop, and thetiming of the pulse is too short (e.g., <0.010 second). Therefore,according to one embodiment of the invention, the sequence in use wouldbe:

-   1. Apply low-level suction to establish the seal of the suction cup    against the lens.-   2. Start the high suction pulse (the mechanical pulse will be slower    than the electrical discharge).-   3. At the peak of suction, discharge the electrical pulse.-   4. Turn off the suction pulse.

In one embodiment, high suction pulse is generated by having the lumenof the stem filled by a piston that can be rapidly moved away from thesuction cup. It does not need to move far (e.g., 0.05 mm to 1 mm if ithas a large cross section). The design should maximize the orifice arealeading to the interior of the suction cup. In one embodiment, a pistonoccupies the stem and an extension (e.g., 1.5 mm wide, 0.1 mm thick)from this piston located above the electrode support ring reaches intothe suction cup (during compression of the suction cup to enter thecorneal incision, the piston is withdrawn up into the stem). Thisextension also has a vacuum channel and orifice to capture the excisedmembrane patch.

FIG. 26 shows a schematic cross section of the applied forces in thevicinity of an electrode. Suction forces on the OD and ID sides of theelectrode clamp the membrane in place against the bottom of the elasticsupport ring. Shear forces are maximized at the corners, so theelectrode is located at a corner (in this case the ID corner) and whenheat weakens the membrane there, the cutting process occurs.Low-pressure regions 205 cause the higher ambient pressure to createforces 209 and 210 acting on the membrane (207), and create clampingareas 202, 203, 204 to immobilize the membrane. When electrode 206 isheated by an electrical discharge, shear force 208 breaks the membranewhere it becomes weakened by thermal breaking of bonds. Suction cup 200simply serves to separate low-pressure regions 205 from the ambientpressure of the surrounding fluid environment.

For pediatric cases, where the membrane does not tear properly withshear forces alone, it may help to use a design that will increase thetensile stress. FIG. 27 shows a schematic cross section with theelectrode (208) located on the bottom surface of the elastic supportring (201). The static stress field set up in the membrane at thatlocation will be more tensile (220). Then when the electrical dischargeoccurs, it can be made to have more energy and achieve a highertemperature to generate more expansive steam pressure within themembrane than would be needed for the adult capsulotomy to providecutting. The forces shown in FIGS. 26 and 27 can apply to any of thedevices described herein.

Alternative Suction Channel Embodiments

Looking at device 300 in FIGS. 28 and 29, piston 301 can be deployed allthe way across the interior of the suction cup 2 (or part way ifdesired). It has a suction channel 302 that is plumbed independently ofthe main suction in the stem 4 with its own source of vacuum. The piston301 slides over the electrode support ring 12. FIG. 29 shows the pistonin its retracted position, as it would be during the compression of thesuction cup to enter the eye. Once in the eye, the piston would bepushed across the suction cup (FIG. 28). To create a pulse of suction,the piston would be rapidly withdrawn to its retracted position (FIG.29) thereby reducing the volume inside the suction cup. Such motionwould not be done manually, but by a spring, or solenoid, or othermechanism. Then the piston would be moved back towards the center of thesuction cup to capture the excised membrane by suction. Then the mainsuction channel would go in reverse to put material into the suction cupto release its hold on the lens.

The above description is included to illustrate the operation of theembodiments and is not meant to limit the scope of the invention. Thescope of the invention is to be limited only by the following claims.From the above discussion, many variations will be apparent to oneskilled in the relevant art that would yet be encompassed by the spiritand scope of the invention. As used herein any reference to “oneembodiment” or “an embodiment” means that a particular element, feature,structure, or characteristic described in connection with the embodimentis included in at least one embodiment. The appearances of the phrase“in one embodiment” in various places in the specification are notnecessarily all referring to the same embodiment.

I claim:
 1. A capsulotomy device for accessing a lens capsule through acornea of an eye, the device comprising: a suction cup; and a cuttingelement attached to the suction cup, the cutting element including: acircular cutting element configured to heat up for excising a portion oftissue of a lens capsule, the circular cutting element along the lengthof the bottom of the cutting element, wherein the cutting element andthe circular cutting element are continuous and made from the samematerial, a plurality of tabs attached to the circular cutting element,the plurality of tabs for securing the cutting element to the suctioncup, and one or more connecting leads attached to the circular cuttingelement, the one or more connecting leads for providing a current to thecircular cutting element to heat the circular cutting element.
 2. Thedevice of claim 1, wherein the circular cutting element is an electricalcutting element, and wherein the device comprises one or more electricalelements for delivering current to the one or more connecting leadsconnected to the electrical cutting element to heat the electricalcutting element.
 3. The device of claim 2, wherein the electricalcutting element comprises a continuous element and wherein the devicefurther comprises a first and second connecting trace connecting theelectrical lead to the electrical cutting element, wherein theconnecting traces are positioned on opposite sides of the electricalcutting element to allow current to travel in two opposite directionsfor conducting current uniformly around the portion of the tissue to beexcised.
 4. The device of claim 1, further comprising one or moresuction elements connected to the suction cup for applying suctionwithin the suction cup.
 5. The device of claim 1, wherein the suctioncup further comprises a flared skirt extending from an edge of thesuction cup for securing the suction cup against the lens capsule toform a vacuum seal.
 6. The device of claim 1, wherein the circularcutting element is an electrical cutting element that is plated onto atleast a bottom side of the cutting element for contacting the lenscapsule to cut free a portion of the tissue of the lens capsule.
 7. Thedevice of claim 1, wherein the plurality of tabs securing the cuttingelement to the suction cup prevents the portion of the cutting elementin contact with the suction cup from forming a complete circuit forcurrent flow.
 8. The device of claim 1, wherein the cutting elementcomprises at least two electrical cutting elements.
 9. The device ofclaim 1, further comprising a stem attached to the suction cup toprovide support between a handle and the suction cup and attachedstructures.
 10. The device of claim 9, wherein the stem compriseselectrically conductive elements for providing current to the cuttingelement.
 11. The device of claim 9, wherein the stem comprises a tubefor applying suction between the suction cup and the lens capsule. 12.The device of claim 9, wherein the stem comprises a support arm.
 13. Thedevice of claim 12, wherein the support arm is electrically conductive,and wherein the support arm is electrically connected to the cuttingelement.
 14. The device of claim 12, wherein the support arm istube-shaped to apply suction between the suction cup and the lenscapsule.
 15. A capsulotomy device for accessing a lens capsule through acornea of an eye, the device comprising: an elastomeric structurecomprising a plurality of openings along the length of the elastomericstructure; and a support structure extending from the elastomericstructure, the support structure comprising a cutting element segmentalong the length of the bottom of the support structure, wherein thesupport structure and the cutting element segment are continuous andmade from the same material, the support structure connecting theelastomeric structure to the cutting element segment, the supportstructure comprising a plurality of tabs attached to the elastomericstructure.
 16. The device of claim 15, wherein the support structurecomprises at least two materials, wherein the material comprising thecutting element segment is more conductive than the material of thesupport structure attached to the elastomeric structure.
 17. The deviceof claim 15, wherein the support structure is discontinuous to inhibitcurrent flow around the path of the support structure attached to theelastomeric structure.
 18. The device of claim 15, wherein the supportstructure is attached to a support arm extending into a stem of thedevice.
 19. The device of claim 18, wherein the support arm isconductive to allow current to flow along the support arm from the stemto the cutting element segment.
 20. The device of claim 18, wherein thesupport arm comprises u-shaped elements extending from the supportstructure, and wherein the u-shaped elements comprise tubes for applyingsuction between the elastomeric structure and the lens capsule.
 21. Thedevice of claim 18, wherein the support arm is tube-shaped for applyingsuction between the elastomeric structure and the lens capsule.
 22. Acapsulotomy device for accessing a lens capsule through a cornea of aneye, the device comprising: an elastomeric structure; and a cuttingelement attached to the elastomeric structure, the cutting elementincluding: a circular cutting element along the length of the bottom ofthe cutting element, wherein the cutting element and the circularcutting element are continuous and made from the same material, aplurality of tabs attached to the cutting element, the plurality of tabsfor securing the cutting element to the elastomeric structure, and oneor more connecting leads attached to the cutting element, the one ormore connecting leads for providing a current to the cutting element toheat the cutting element.